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Variables and lists

Variables store a single value (a number or a piece of text). Lists store many values in order. Both live in the Variables category of the block palette, and both are created with the buttons at the top of that category.

Making a variable​

  1. Open the Variables category in the block palette.
  2. Click Make a Variable.
  3. Type a name and choose a scope (see below).
  4. Click OK.

Your new variable appears in the palette with set, change, show, and hide blocks, plus a reporter block you can drop into any input.

Lists work the same way: click Make a List instead. A list comes with blocks to add, delete, insert, replace, and read items, and to check its length and contents.

Scope: all sprites vs this sprite​

When you make a variable or list you pick one of two scopes:

  • For all sprites (global): every sprite and the Stage shares the same variable. Changing it from one sprite changes it everywhere. Use this for things like a score or a game state that the whole project cares about.
  • For this sprite only (local): the variable belongs to the sprite that is currently selected. Other sprites cannot see it, and each clone of the sprite gets its own private copy. Use this for per-sprite data like health or speed.

The Stage can only hold global variables, because it has no clones and nothing "local" to belong to.

note

Two sprites can each have a local variable with the same name without clashing, because they are genuinely separate variables. A local variable and a global variable can also share a name; the local one takes priority inside its sprite.

Monitors on the stage​

Every variable and list has a monitor, the small readout shown on the stage. Toggle it by checking the box next to the variable in the palette, or with the show variable / hide variable blocks.

  • Drag a monitor anywhere on the stage to reposition it.
  • Right-click a variable monitor to switch between the normal readout, a large readout, and a slider you can drag to change the value live.
  • Right-click a list monitor to resize it or export/import its contents.

Monitors are saved with the project, so their position and style travel with it.

Advanced notes​

  • Variable and list values are stored as JavaScript strings and numbers. The compiler reads and writes them directly, so large lists are fast, but very large lists still cost memory and save time.
  • List comparisons are case-insensitive by default. The Case Sensitive Lists option in Settings makes "a" and "A" distinct values, which can speed up list-heavy projects at the cost of vanilla compatibility.
  • To view or bulk-edit every variable and list at once, use the Variable Manager.

See also​